Lubricating compositions containing borate ester-amine complexes



United States Patent "cc 3,200,074 LUBRICATING COMPGSITIONS CONTAINING BORATE ESTER-AMHNE COMPLEXES Edwin C. Knowles, Poughlreepsie, N.Y., and Edward L. Kay, Akron, Ohio, assignors to Texaco Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed May 20, 1963, Ser. No. 281,824

14 Claims. (Cl. 25249.6)

, This application is a continuation-in-part of application Serial No. 59,180, filed September 28, 1960, and now abandoned.

This invention relates to a novel class of lubricant additives and to lubricant composition containing them.

More particularly, it relates to lubricating compositions containing borate ester-amine complexes.

We have found, in accordance with this invention, that stable complexes comprising a very valuable class of lubricating oil additives are obtained by treating borate esters with higher aliphatic amines. These complexes comprise a particularly suitable class of boron compounds for use in formulating lubricant compositions for the lubrication of the so-called transaxle units in automotive vehicles, in accordance with the invention of E. L. Kay, R. B. Tierney, R. H. Krug and C. J. Henry, disclosed and claimed in their copending application Serial No. 59,179, now Patent No. 3,125,528, patented March 17, 1964. As disclosed therein, it Was found that certain organic boron compounds, including borate esters particularly, provide the load carrying and anti-scufling properties required for hypoid rear axle gear lubrication in lubricating oils without impairing the properties required for automatic transmission lubrication. The borate esteramine complexes of the present invention impart very effective anti-corrosiveness and detergency to lubricating oils, as required for automatic transmission lubrication, while having substantially equivalent load bearing and anti-scufling properties to the borate esters on an equimolar basis. In addition, the borate ester-amine complexes are very much superior to the borate esters in hydrolytic stability, and they therefore offer aconsiderable advantage in lubricating composition which are employed in the presence of water or which may become contaminated by Water, such as crankcase oils.

The exact nature of the complexes formed by treating borate esters with aliphatic amines is not fully understood. Ordinarily, the reaction takes place exothermally in accordance with the usual phenomenon of adduct formation, but in some cases no evolution of heat is found. However, even where there is no evolution of heat, a relatively stable association complex of some type is formed, having materially different properties from those of the separate components. Aryl borate esters and amines normally react to form adducts in a 1:1 mol ratio. However, we have'found that complexes obtained by reacting borate esters and amines in proportions far below the normal 1:1 ratio, such as in proportions down to about 1:0.1, respectively, have substantially equivalent hydrolytic stability and other advantages as lubricating oil additives. It is advantageous for some purposes to employ these smaller amounts of amine, the complex being preferably formed employing the borate ester and amine in a mol ratio between about 120.5 to about 1:02, respectively.

The borate esters which are employed for forming these complexes are compounds of the class represented by the formula: B(OR) wherein R is selected from the class consisting of hydrocarbon groups and halogen substituted hydrocarbon groups. Hydrocarbon groups which may be represented by R include alkyl, aryl, alkaryl and aralkyl groups and the halogen substituted derivatives of these groups.

32%,574 Patented Aug. It), 1965 A preferred class of borate esters for forming the borate ester-amine complex comprises esters represented by the above-noted formula in which at least one R is a halogenated hydrocarbon group, and more specifically a halogenated aryl group, such as a halophenyl group.

A more specifically preferred class of the borate esters comprises esters of the above-noted formula in which two Rs are halogenated hydrocarbon groups and the remaining R is an alkaryl group or a hydroxyalkaryl group in which the alkyl radical has from 4 to 30 carbon atoms.

Examples of suitable compounds of the above class include the following: trimethyl borate, tri-n-propyl borate, tri-isobutyl borate, tristearyl borate, triphenyl borate, tri-p-chlorophenyl borate, tri(nonylphenyl) borate, di(2-ethyl-hexyl) nonylphenyl borate, tricresyl borate, tribenzyl borate, tri-2-phenylcyclohexyl borate, tri(diisobutylcarbinyl) borate, mono-nonylphenyl-di-(2,4-dichlorophenyl) borate, dibutyl-p-chlorophenyl borate, di-pchlorophenyl-mono-p-nonylphenyl borate, di-p-chlorophenyl-mono-p-dodecylphenyl borate, di- (monylphenyl)- mono-pentachlorophenyl borate, tri-dodecylphenyl borate, tri-p-chlorophenyl borate and di-chlorophenyl-mono-octadecyl borate.

The aliphatic amines which are employed to form the borate ester adducts are compounds of the class comprising aliphatic mono-amines containing at least six aliphatic carbon atoms and up to twenty-six aliphatic carbon atoms per molecule wherein the amine groups may be primary, secondary or tertiary amine groups. Examples of suitable amines include dodecyl amine, tertiary tetradecyl amine, tertiary undecyl amine, secondary dibutyl amine, octylamine, and hexadecylamine. The preferred compounds are monoamines containing from about 8 to 26 aliphatic carbon atoms per molecule, particularly suitable compounds being primary amines wherein the alkyl group is a tertiary alkyl group.

Formation of the borate ester-amine complexes takes place readily over a Wide range of conditions. The complexes may be prepared by merely mixing together the borate ester and amine in the reacting proportions at room temperature or at moderately increased temperatures in the presence or absence of a solvent. The reaction may be carried out in situ if desired in the presence of at least a portion of the lubricating oil employed in the composition.

The borate ester-amine complexes are ordinarily em-' ployed in lubricating oils in amounts in about the range 0.-l10 percent by weight, based on the weight of the composition, although somewhat larger or smaller amounts may be employed if desired. They are preferably employed in amounts in about the range O.55 percent by weight. The lubricating composition may also contain other additives of various types, such as are commonly employed in lubricating compositions such as other extreme pressure agents, anti-corrosives, anti-oxidants, pour depressants, viscosity index improvers, etc., where no ad verse effect results from their use in conjunction with the borate ester-amine complex.

Lubricating oils in which the borate ester-amine complexes may be employed include conventional mineral oils and synthetic oils, such as high molecular weight ethers, esters, silicones, etc. Suitable mineral oils include both paraffinic and naphthenic oils and blends thereof, having viscosities in the range from about seconds Saybolt Universal at F. to about 225 seconds Saybolt Universal at 210 F. Mineral oils having viscosities in about the range 40 to about 50 seconds Saybolt Universal at 210 F. are preferred for the production of automotive transmission lubricants in accordance with the preferred embodiments of this invention. A particularly suitable class of synthetic lubricating oils comprises synthetic dicarboxylic acid esters, such as di-2-ethylhexyl sebacate, (di-secondary amyl) sebacate, di-Z-ethylhexyl azelate, etc. and polymers obtained by condensing dicarboxylic acids with glycols as disclosed in US. 2,628,974, as well as the sulfur analogs of such esters. Other synthetic oils which may be employed in accordance with this invention include the silicone polymers, including dialkyl silicone polymers such as dimethyl silicone polymer, diethyl silicones and mixed aryl alkyl silicone polymers such as phenyl methyl silicone polymer, having viscosities in the lubricating oil viscosity range.

Lubricating compositions containing the borate esteramine complexes which are to be employed as automatic transmission lubricants may very advantageously contain a detergent additive, very suitably of the class consisting of metal salts of acidic organic compounds having high solubility in lubricating oils, particularly those wherein the metal component is a member of the group consisting of alkali metals, alkaline earth metalsand zinc. Suitable acidic materials for producing these compound include particularly sulfonic acids having molecular weights in about the range 350-450, alkyl phenols containing at least one alkyl group containing at least four carbon atoms, and preferably at least eight carbon atoms, sulfides of such alkyl phenols wherein two phenol nuclei are connected by one or more sulfur atoms, and olefin polymer-phosphorous sulfide reaction products wherein the olefin polymer has a molecular weight of about 500-1500. The lubricant composition may very suitably contain at least one detergent compoundof thisclass in an amount of about 0.110 percent by weight of the composition. Suitable oxidation inhibitors for use in these compositions include particularly alkyl phenols, such as 2,6-ditertiary-butylA-methyl phenol, arylamines, amino phenols, etc. Such compounds may be suitably employed in amounts up to about percent by weight, and most advantageous-1y in amounts of about 0.22 percent by weight based on the weight of the composition.

Viscosity index improvers which may very advantageously be employed in automatic transmission fluids containing the borate ester-amine comlexes include principally polymeric materials of various types, including olefin, diolefin, mixed olefin-diolefin, olefin styrene, etc., polymers and ester type polymers such as acrylates, methacrylates, maleic of furnaric ester-vinyl acetate copolymers, etc., wax alkylated naphthalene, etc. Particularly suitable materials of this type are the methacrylate polymers, having molecular weights in the range from about 5000 to about 75,000, which are sold commercially under the trade name Acryloid. The preferred polymeric materials are those having molecular weights of about 10,00020,000. The lubricating composition may suitably contain about 0.55.0 percent by weight of such polymer viscosity index improver, preferably in an amount suifiificient to obtain a composition having a viscosity indexof at'least about 125.

The following examples are given for the purpose of further disclosing the invention.

Example I A tribenzyl borate-amine association complex was prepared by reacting together tribenzyl borate and a high molecularweight aliphatic amine in a 1:1 mol ratio. The tribenzyl borate was obtained by reacting 171 grams (2.77 mols) of boric acid and 897 grams (8.31 mols) of benzyl alcohol in the presence of 500 ml. of toluene as a solvent. The water of reaction was removed by atmospheric distillation of the solvent-water azeotrope and toluene subsequently removed by atmospheric distillation. The product was a clear yellow liquid. The amine employed was a commercial material sold by Rohm & Haas under the trade name of Primene 81-R consisting of tertiary alkyl primary amines in the range from C I-1 N11 to C H NH Synthesis of the association complex was carriedout by adding 213 grams of the amine dropwise to 332 grams of the tribenzyl borate in a glassflask at room temperature with stirring, the stirring being continued for about 30 minutes after addition of the amine was completed. The reaction took place with no change in temperature. A light yellow liquid was obtained which was oil soluble and stable in the presence of water during storage for two weeks. The anti-corrosive properties of this compound are shown by the test results given below. The base oil employed was a highly refined parafiinic distillate oil having a Saybolt Universal viscosity at 210 F.-of about 47 seconds.

MACGOULL CORROSION TEST 350 F., Cu-Pb. bearing 10 hrs. 7 Composition Neut. N0.

Wt. loss, Mg.

. used oil Base 011 28 1. 1 Base oil plus 1.0% tribenzyl borate amlne 11 0.9

The complex formation was also carried out employing varying ratios of borate ester to amine. A hydrolytically stable product was obtained with borate ester-amine mol ratios as low as 120.10, as shown by the following table. In contrast to .the hydrolytic stability of the complex, the borate ester alone begins to separate boric acid almost immediately in the presence of water.

Adduct composition Adduet stability.

Appearance after] days storage M01 ratio of borate ester to amine 'Dry Over water Clear.

Solid separated;

Example II A trimethyl borate-amine complex was formed by reacting v412 grams of trimethyl borate with 780 grams of the amine described in Example I. The reaction took place exothermically with a temperaturerise from the initial temperature of 77 F. to 86 F. The product was a clear light yellow liquid.

The above product was hydrolytically stable and had superior anti-corrosiveness as shown by the test results given below. The base oil was a 660 viscosity SUS at F. blend of a refined paraffinic residual oil and a refined paraffinic distillate oil.

MACCOULL CORROSION TEST 350 F., Cu-Pb. bearing, 10 hrs. Composition Wt. loss, Mg. Neut.N0.

used oil Base oil I V 61 Base 011 plus 2.0% trimethyl borate 82 Base 011 plus 2.0% trimethyl borate amine. I 45 Example III 7 cally, yielding a product which was a clear dark amber viscous liquid.

The following table shows the anti-corrosive properties of the above product in comparison with those of the borate ester alone and of the amine alone. The base oil employed in the compositions was a refined paraffinic blend of residual and distillate oils having a Saybolt Universal viscosity at 100 F. of about 660 seconds.

MACCOULL CORROSION TEST 350 F., Cu-Pb. bearing, hrs. Composition Wt. loss, Mg. Neut. No.

used oil Base oil 96 5. 6 Base oil plus 0.92% amine 193 5. 9 Base oil plus 1.15% amine 220 6.0 Base oil plus 2.31% tri-(nonylphenyl) borate 105 6. 3 Base 011 plus 3.08% trl-(nonylphenyl) borate 28 6.3 Base oil plus 3.0% trl-(nonylphenyl) borate amine 0 3. 2

In addition to their anti-corrosive properties as shown above, these complexes also have good extreme pressure properties of the type required for the lubrication of rear axle hypoid gears in automotive vehicles, as shown by the following table. The base oil employed in the compositions was a 100 SUS viscosity at 210 F. blend of refined paraffinic residual and distillate oils.

IAE gear test (200 r.p.m.

Composition: tooth lead, lbs.

Base oil 100 Base oil +20% trimethyl borate amine 200 Base oil +20% tri-(nonylphenyl) borate amine (200 lbs. is maximum load of IAE gear rig.)

The IAE gear test shown in the above table is a test 'for measuring the load bearing properties of lubricants 100 hrs. at 325 F.

Composition Viscosity in- Neut. No. crease (Kin. increase at 100 F.)

borate O. 78 30 Base oil 1.25% amine 0.81 24 Base oil 5.0% tri-(nonylphenyl) borate amine 0.05 4. 9

CHEVROLET S-iA ENGINE TEST Cleanliness Neut. No. of Viscosity of oil merit oil at hr. SUS at 210 F. Composition rating total at hr.

Base oil 72. 0 0. 08 6.3 54 76. 9 Base oil plus 4.0%

tri-(nonylphenyl) borate amine 89. 2 0. 22 1. 8 52. 8 58. 3

9 Based on 100 as perfect.

Example IV' An adduct of di-(nonylphenyl)-mono-pentachlorophenyl borate was prepared in the following manner: The borate ester was prepared by refluxing together 61.8 grams of boric acid, 440.0 grams of nonylphenol and 500 ml. of xylene for 13.5 hours, until the theoretical amount of Water was obtained, 266.4 grams of 2,3,45,6- pentachlorophenol were then added and the mixture refluxedfor an additional 229.5 hours until the theoretical amount of water was again obtained. The product was isolated by removal of the solvent under reduced pressure. A dark brown viscous liquid was obtained in an 84.7 percent yield, analyzing 1.449 percent boron and 24.3 percent chlorine. The amine employed was that described in Example I. The borate ester and amine were reacted in a mol ratio of 1:1 in the manner described in Example I. The product obtained as described above was non-corrosive to copper in the ASTM Copper Corrosion Test at 210 F. and had superior extreme pres sure properties as shown by the test results given below. The base oil was a blend of refined paraffinic distillate and residual oils containing about 0.1 percent of a methacrylate polymer pour depressant and having a Saybolt Universal viscosity at 210 F. of about 93 seconds.

EXTREME PRESSURE TESTS Base oil +30% di- Composition Base Oil nonylphenyl-mono- I pentachlorophenyl borate amine Mean Hertz Load, Kg. 2e 35 SAE test, 500 r.p.m. lb.-- 372 Example V An amine adduct of di-p-chlorophenyl-mono p-nonylphenyl borate was prepared in the following mannerpThe borate ester wasprepared by refluxing together 185.5 grams of boric acid, 660.0 grams of nonylphenol and 250 ml. of xylene for 2.25 hours until 58 ml. of water were obtained. 771.0 grams of p-chlorophenol were then added, and the mixture refluxed for an additional 212 hours 103 ml. of water were obtained. The solvent was thereafter removed under reduced pressure. 573 grams of the amine described in Example I were added to the borate ester dropwise with stirrring and the stirring continued for 2 hours. A temperature rise of 38 C. was observed during the amine addition. The product obtained was a clear yellow, very viscous liquid, obtained in over 99 percent yield. The following tabulation shows gear oil tests obtained upon a lubricating oil containing the above compound:

An amine adduct of di-p-chlorop-henyl-monoa('alkyl-ocresyl) borate was prepared by a single step esterification of boric acid with p-chlorophenol and alkyl-ocresol in a mol ratio of 1:221, respectively, employing cumene as a water entrainer. The alkyl-o-cresol employed was a product obtained by alkylating o-cresol with propylene tetramer comprising chiefly p-dodecyl-ocresol. The reaction mixture was refluxed for 34 hours to a maximum pot temperature of 364 F. and the cumene then stripped otf under reduced pressure. The

amine adduct of the borate ester thus obtained was prepared by adding the amine described in Example I dropwise with stirring and with the temperature maintained below 150 F., employing the borate ester and amine in a 1:1 mol ratio.

The above compound has very effective anti-corrosive and anti-wear properties in both mineral and synthetic lubricating oils, substantially equivalent to those of the di-p-chlorophenyl-mono-nonylphenyl borate adduct, and in addition it is particularly outstanding in its hydrolytic stability.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A lubricating composition comprising a lubricating oil in major proportion and about 0.1-10.0 percent by Weight based on the weightof the composition of a complex of a borate ester and an aliphatic amine in a mol ratio of :1 to 1:1, respectively, said aliphatic amine being selected from the class consisting of alkyl monoamines containing from 6 to 26 aliphatic carbon atoms per molecule and said borate ester being a compound of the class represented by the formula: B(OR) wherein R is selected from the class consisting of hydrocarbon groups and halogen substituted hydrocarbon groups, said groups having from 1 to 18 carbon atoms.

2. A lubricating composition according to claim 1 in which at least one R is a halogenated hydrocarbon group.

3. A lubricating composition according to claim 1 in which at least two Rs are halogenated aryl groups and the remaining R is selected from the class consisting of an alkaryl group and a hydroxyalkaryl group in which the alkyl radical has from 4 to 30 carbon atoms.

4. A lubricating composition according to claim .1 wherein said aliphatic amine is a tertiary alkyl primary monoamine containing about 8-26 aliphatic carbon atoms per molecule.

5. A lubricating composition according to claim 1 wherein the said borate ester and said amine are in a mol ratio in the range from 5:1 to 2:1, respectively.

6. A lubricating composition according to claim 1 wherein the said borate ester and said amine are in a mol ratio of about 1:1. I

7. A lubricating composition according to claim 1 (alkyl-o-cresyl) borate, said alkyl group containing about 4-30 carbon atoms.

11. A lubricating composition accordingt-o claim 10 wherein the said aliphatic amine is atertiary alkylprimary monoamine containing about, 12-15 carbonatoms per molecule, said borate ester and said amine being present in a 1:1 mol ratio.

12. A lubricating composition comprising a lubricating oil in major proportion and about 0.1 to 10.0 percent by weight based on the weight of the composition of a complex of a borate ester and an aliphatic amine in a mol ratio of 10:1 to 1:1, respectively, said aliphatic amine being selected from the class consisting of. alkyl monoamines containing from 6 to 26 aliphatic carbon atoms per molecule and said borate ester being a compound of the class represented by the formula: B(OR) in which at least one R is a halogenated aryl group having from 6 to 18 carbon atoms and at least one R isselected from the class consistingof an alkaryl group and a hydroxyalkaryl in which the alkyl radical has from 4 to 30 carbon atoms.

13. A lubricating composition according'to claim 12 inwhich at least one'R is a chloroaryl group.

14. .A lubricating composition according to claim 12 in which two Rs are chlorophenyl groups.

References Cited by the Examiner UNITED. STATES PATENTS 2,234,581 3/41 Rosen 25.2-49.6 2,312,208 2/43 Clayton ct a1 25249.6 XR 2,961,443 11/60 Ashby et a1; 252-496 XR 3,108,966 10/63 Dadura 25246.3 3,125,526 3/64 Siegart et al. 252'40.7 3,125,528 3/64 'Kay et a1 252-49.6

DANIEL E. WYMAN, Primary Examiner. 

1. A LUBRICATING COMPOSITION COMPRISING A LUBRICATING OIL IN MAJOR PROPORTION AND ABOUT 0.1-10.0 PERCENT BY WEIGHT BASED ON THE WEIGHT OF THE COMPOSITION OF A COMPLEX OF A BORATE ESTER AND AN ALIPHATIC AMINE IN A MOL RATIO OF 10:1 TO 1:1, RESEPECTIVELY, SAID ALIPHATIC AMINE BEING SELECTED FROM THE CLASS CONSISTING OF ALKYL MONOAMINE CONTAINING FROM 6 TO 26 ALIPHATIC CARBON ATOMS PER MOLECULE AND SAID BORATE ESTER BEING A COMPOUND OF THE CLASS REPRESENTED BY THE FORMULA: B(OR)3, WHEREIN R IS SELECTED FROM THE CLASS CONSISTING OF HYDROCARBON GROUPS AND HALOGEN SUBSTITUTED HYDROCARBON GROUPS, SAID GROUPS HAVING FROM 1 TO 18 CARBON ATOMS. 